1. Field of the Invention
The present invention relates to an endoscope system for displaying information on oxygen saturation of hemoglobin in blood and information on blood volume, a processor apparatus of an endoscope system, and a method for generating images.
2. Description Related to the Prior Art
Recently, diagnoses using an endoscope have been performed commonly. In addition to normal observation of a portion of a subject using an endoscope apparatus with illumination of broadband light (white light), special observation using illumination of narrowband light has come into practice. By using the narrowband light, blood vessels in the portion being observed are highlighted in display.
Furthermore, functional information such as oxygen saturation of hemoglobin in blood and blood vessel depth is obtained from an image signal from an endoscope apparatus. The functional information is obtained based on light absorption property of blood vessels and scattering property of a living tissue. Then, an image representing the functional information is generated. For example, in Japanese Patent No. 2648494, colors are assigned according to different oxygen saturation levels. A pseudo-color oxygen saturation image is generated based on the colors assigned. Such oxygen saturation image facilitates finding, for example, a cancer causing the oxygen saturation specifically low. Accordingly, diagnostic performance improves.
Out of cancers causing a low-oxygen or hypoxic condition, an undifferentiated early gastric cancer causes blood density (the blood volume) in a tumor area extremely low compared with well-differentiated cancer. To find the undifferentiated early gastric cancer without fail, it is desired to obtain information on the blood volume from the image signal, in addition to the information on the oxygen saturation. The Japanese Patent No. 2648494, on the other hand, is only capable of obtaining the oxygen saturation. Accordingly, it is difficult to find a lesion site such as the undifferentiated early gastric cancer characterized by both the oxygen saturation and the blood volume.